17-haloyohimbanes



United States Patent 3,215,698 17-HALOYOHIMBANES John Shave], Jr., Mendham, Maximilian von Strandtmann,

Rockaway Township, and George Bobowski, East Orange, N.J., assignors to Warner-Lambert Pharmaceutical Company, Morris Plains, N.J., a corporation of Delaware No Drawing. Filed Apr. 1, 1963, Ser. No. 269,791

8 Claims. (Cl. 260288) The present invention relates to new and novel 17- haloyohimbanes having the formula:

D W E 1; 1 and wherein R may be hydrogen or R may be hydrogen or lower alkyl such as methyl or ethyl or a 'chlorornethyl group, X is halogen such as chlorine, bromine or fluorine, and X may be fluorine or chlorine. This invention also relates to -a process for the production of said l7-ha1oyohimbanes and to new and novel intermediates for their production.

The compounds of this invention are useful as tranquilizers. In addition, they are valuable intermediates in the production of other alkaloids of the yohimbane series.

The compounds of this invention, which bear the A, B, C, D and E rings as depicted in the above structural formulas, are generally 17-halo derivatives of alkaloids of the yohimbane series. Thus, the dotted lines at C/D and D/E ring junctions denote alpha configuration. The C hydrogen is generally beta-oriented and is indicated by the use of a dot at position 20. The substituents at positions 16 and 17 can also be alphaor beta-oriented. The use of a dotted line in the above structural formulas denotes alpha-orientation and the use of a solid line, beta-orientation.

"ice

The starting materials for the production of the compounds of our invention have the formula:

III

epiyohimbol 16a-methylyohimb0l and lfia-chloromethylyohimbol by known procedures.

It has been found that the 17a-haloyohimbane derivatives may be prepared by the following sequence of reactions:

epiyohimbol l p-toluenesulfonyl chloride lHF The initial step in the production of 17a-haloyohimbane derivatives is the conversion of epiyohimbol to 17,8- (p-toluenesulfonyloxy)-yohimbane by reacting with ptoluenesulfonyl chloride. This reaction may be carried out in anhydrous pyridine at a temperature of about to 4 C.

The product obtained is then reacted with the selected hydrogen halide (such as hydrogen bromide or hydrogen fluoride) to obtain the desired 17a-haloyohimbanes. This halogenation reaction is also preferably carried out under anhydrous conditions in a suitable solvent such as pyridine.

An alternate pathway to the preparation of 17m-haloyohimbanes is by the direct action of a phosphorous oxyhalide such as phosphorous oxychloride on epiyohimbol.

The 17a-haloyohimbanes obtained in accordance with the above process are readily converted to -acy1 substituted l7a-haloyohimbane by treating the former with an acetylating agent such as acetic anhydride, in the presence of boron-trifluoride.

The present invention, therefore, embraces not only the 17u-haloyohimbanes, but also 10-acyl-substituted derivatives thereof.

It has also been found that the 17fl-haloyohimbane derivatives may be produced by the following sequence of reactions employing 16a-methylyohimbol as the starting material and analogous reaction conditions for the production of 17a-haloyohimbanes described above.

lfia-methylyohimbol lp-toluenesulfonyl chloride Generally, the desired l7ocand ,B-halo-substituted yohimbanes, are extracted from the reaction mixture by basifying the latter with ammonia or sodium hydroxide. The precipitate obtained is purified by recrystallization from methanol or ethyl acetate.

The following examples are included further to illustrate the present invention, all temperatures being given pyridine is added dropwise to a solution of 8.0 g. of epiyohimbol in 25 ml. of anhydrous pyridine over a period of 15 minutes With stirring at 0. The cooling bath is removed, and the solution is allowed to stand for four hours at 20 to 25 C. 200 ml. of ether are then added with stirring and the resulting precipitate is filtered off,

: solvent is removed in vacuo.

made basic with ammonia, taken up with 150 ml. of chloroform and the two phases separated. The aqueous layer is extracted with ml. of chloroform. The combined extracts are dried over anhydrous sodium sulfate and the Trituration with 15 ml. of hot tetrahydrofuran-methanol (2:1) and recrystallization from methanol-tetrahydrofuran (1:1) gives 17B-(p-toluenesulfonyloxy)-yohimbane, M.P. 285293, yield: 4 g., [a] :+5, c.:0.46, chloroform; [a] :17,

: c.:0.69, pyridine.

Anal. for C H N O S.Calcd.: C, 69.30; H, 6.71; N, 6.22; S, 7.12. Found: C, 69.07; H, 6.62; N, 6.23; S, 7.04, 6.84.

Infrared spectra, 1152131213470 (s), 1599, 134.5 (v.s.), 1173 (v.s.), 955 (W.) 918 (V.S.), 871 (V.S.), 839 (m.) 816 (m.), 663 (m.) 31117 U. V. spectra, XEZQF: 225 mu (=7,350), shoulder: 289 m (e=4.-7,000), 276 mu (e=7,350); shoulder: 289 mn(e=6,050); min.: 2455 my. (=2,350).

To a solution of 3.0 g. of 17/3-(p-toluenesulfonyloxy)- yohimbane in 25 ml. of dry pyridine, in a polyethylene container, protected from moisture, is added 25 ml. of hydrogen fluoride while keeping the temperature at 20 and the reaction is allowed to proceed at 20 to 25 for about eight days. The contents are poured onto 400 g. of crushed ice and made basic with ammonia. The solid which precipitates is filtered ofl and taken up with 200 ml. of methylene chloride. The solution is treated with charcoal, dried, and the solvent removed in vacuo. Trituration of the brown-greenish, solid residue with 15 ml. of hot methanol and recrystallization from methanol gives 17oc-fluoroyohimbane in the form of white crystals, M.P. 203-220", [a] :9l, 0.20.82, chloroform; [oc] :-108, c.:0.9, pyridine.

Anal. for: C H N F.Calcd.: C, 76.47; H, 7.77; N,

5 9.39; F, 6.37. Found: C, 76.95, 76, 67; H, 7.60, 7.85; N, 9.44; F, 6.30, 6.40.

Infrared Spectra, 11222: 1263 (m.), 1119 (vs), 961 (vs), 897 (v.s.), 835 (s.) cm. U.V. spectra, AEEEF: 225 m (e=34,500), 280 mp (e=6,800); A595, 288 mp (e=5,750); A min: 245 m (e=1,600).

Example 3 .1 7 a-bromoyohimbane To a stirred solution of 8.0 g. of '17/8(p-toluenesulfonyloxy)-yohimbane in 150 ml. of anhydrous pyridine, protected from moisture and heated on a steam bath at 75 (internal temperature) gaseous hydrogen bromide is introduced over a period of forty minutes. The heating is continued for five hours at 85. After the reaction mixture is cooled to 5, it is then poured onto 2 liters of icewater, made basic with ammonia, and the tan-brown colored precipitate is filtered off and re-dissolved in chloroform. The chloroform solution is dried over anhydrous sodium sulfate, and the solvent is removed in vacuo. Trituration of the brown residue with 20 ml. of hot methanol yields 2.0 g. of l7a-bromoyohim-bane. Recrystallization from methanol and methanol-acetone (1:1) gives white crystals, M.P. -2'92-297, [a] =56, c.=0.6, chloroform; [u] ==83, c.=0.8, pyridine.

Anal. for: C H N Br:Calcd.: C, 63.51; H, 6.45; N, 7.80; Br, 22.24. Found: C, 63.73; H, 6.50; N, 7.63; Br,

(e=37,600), 280 m (e=7,250); Ashoulder: 287 m (e=6,100); A min.: 246 my. (e=l,900).

Example 4 .-1 7 a-chloroyohimbane Method A.Gaseous hydrogen chloride is bubbled through a heated solution (about 70 C.) of 0.8 g. of 17 8- (p-tolnenesulfonyloxy) yohimbane in 20 ml. of anhydrous pyridine over a period of 15 minutes. After heating for an additional half hour, the hot solution is poured onto 1 20 g. of crushed ice, made basic by ammonia and filtered. The tan-colored solid is redissolved in methylene chloride, dried over sodium sulfate, and the solvent removed in vacuo. Crystallization of the brown residue from methanol gives 0.45 g. of 17a-ch1oroyohimbane in the form of tan-colored needles, M.P. 195-198 '(the melted product resolidifies at 215, and remelts at 300304 [a] =-42.6, c.=0.75, chloroform; [a] =49, c.=0. 865, pyridine.

Anal. for: C H N Cl.Calcd.: C, 72.48; H, 7.36; N, 8.90; Cl, 11.26. Found: C, 72.55; H, 7.49; N, 9.10; Cl, 11.09, 10.97.

Nuiul.

Infrared spectra, p 1253 (m.), 729 (vs), 717 (s.) cmf U.V. spectra, A

225.5 m (e=38,750), 282 m (e=7,650); A shoulder: 288 m (e=6,400); Amin.: 246 m (6=2,4;0O).

Method B.-A solution of. 4.2 g. of p-toluenesulfonyl chloride in 15 ml. of dry pyridine is added with stirring at to a solution of 6.0 g. of epiyohimbol in 25 ml. of pyridine over a period of 30 minutes and is allowed to stand at 20 to 25 C. for one half hour. The mixture is then heated on a steam bath about 70 to 80 (CaCl tube), and gaseous hydrogen chloride is bubbled in for 20 minutes. After the heating for an additional five hours, the brown-black solution is poured onto 300 g. of crushed ice and the resulting precipitate is filtered ofi. The collected dark residue is stirred with 25 ml. of aqueous sodium hydroxide in 150 ml. of chloroform, and the two phases are separated. The chloroform extract is dried over anhydrous sodium sulfate, and the solvent is removed in vacuo. T rituration of the brown-black residue with 10 ml. of methanol gives 2.9 g. of 17a-chloroyohimbane. The product is further purified by dissolving in acetonemethanol (2:1), treatment with charcoal, and concentration to a low volume to give white needles, M.P. 195 to 200 (resolidifies at 220, remelts at 295 to 303),

6 :-40, c.=0.7, chloroform; [a] =-48, c.=0.45, pyridine.

Example 4 Method C.-To a chilled solution of 4 g. epiyohimbol in -20 ml. dry pyridine is added with stirring and under protection from moisture a solution of 7 ml. P001 in 20 ml. pyridine. After heating on a steam bat-h at about 75 to for minutes, the black reaction mixture is poured into 300 ml. ether. The oily precipitate is triturated with two ml. portions of ether and dissolved in 300 ml. water. The solution is basified with ammonia. The precipitated product is dissolved in the minimum amount of acetic acid and the resulting solution is diluted with 600 ml. water. After adjusting the pH to 5 by addition of ammonia, the mixture is filtered over supercel. The filtrate is basified with ammonia and the resulting precipitate dried and dissolved in acetone. This solution is decolorized with charcoal and concentrated in vacuo to give 17a-chloroyohimbane in the form of crystals melting at 17-8 to 185; [a] =-51, c.=0.8, pyridine.

Anal. for: C H N Cl.Calcd.: C, 72.48; H, 7.36; N, 8.90; Cl, 11.26. Found: C, 72.53; H, 7.50; N, 8.95; Cl, 11.27.

Example 5.--10acetyl-17ot-chl0r0y0himbane Method A.A solution of 3.0 g. of 17a-chloroyohimbane in 10 ml. of glacial acetic acid and 60 ml. of acetic anhydride is added dropwise with stirring at 10 to a mixture of 10 ml. of glacial acetic acid and 100 ml. of acetic anhydride, saturated previously at 10 with borontrifluoride gas. After the stirring is continued for four hours at 15 to 5, the contents are poured onto 500 g. of crushed ice, made :basic by ammonia, and extracted twice with ml. of chloroform. The extracts are dried over sodium sulfate, and the solvent is removed in vacuo. The brown semi-solid residue is chromatographed on 120 g. of florisil (8 fractions, 50 ml. each), using methylene chloride and, finally, methanol as eluents. The combined eluates of fractions 3-8 are evaporated to dryness under reduced pressure, and the residue is recrystallized from acetonitrile to give 1.4 g. of 10-acetyl- 17a-chloroyohimbane in the form of white crystals, M.P. 2 20 to 225, [a] =36, c.=0.595, chloroform; [a] =18, c.-=0.8, pyridine.

Anal. for: C H N OCl.Calod.: C, 70.67; H, 7.06; N, 7.85; Cl, 9.94. Found: C, 70.68; H, 7.20; N, 7.59; Cl, 10.18, 10.08.

Nuiol.

Amin.: 225 m (e=4,250), 276 m (e=7,000).

Example 6 .1 6u-methyl-1 7on (p-toluenesulfonyloxy yohimbane To a solution of 9.3 g. 16a-methylyohimbol in 50 ml. dry pyridine is added with stirring a solution of 18.6 g. p-toluenesulfonylchloride in 20 ml. pyridine. The reaction mixture is stirred for half an hour, allowed to stand 16 to 18 hours at 20 to 25 C. and poured into 250 ml. ice-cold 1% sodium hydroxide. The precipitate is filtered off, washed with water, suspended in ca. 200 ml. 5% ammonia and 200 ml. chloroform and stirred for one hour. The solids are collected on filter, dried in a vacuum desiccator and recrystallized from acetonitrile, giving methyl 17u(p toluenesulfonyloxy)yohimbane, M.P. 290 to 3295"; [a] =50, c.=0.7, pyridine.

Anal. for: C H N O S0 /2H O.Calcd.: C, 68.46; H, 7.02; N, 5.92; S, 6.77. Found: C, 68.36; H, 6.82; N, 5.65; S, 6.48.

max.

(e=7,000); A shoulder: 290 (e=6,000) m Example 7.17,8-chlr0-16amethylyohimbane Into a solution of 3 g. 16a-methylyohimbol(p-toluenesulfonyloxy)yohimbane in 20 ml. dry pyridine a stream of dry hydrogen chloride is introduced without cooling and under the protection from moisture. The reaction mixture is then heated to about 80 on a steam bath for about four hours, allowed to cool, poured into 600 ml. ice-water and basified with 2% sodium hydroxide to give 175-chloro-16a-methyly0himbane as a precipitate which is collected on filter and dried in a vacuum desiccator over sulfuric acid. Yield: 1.4 g. A twofold recrystalliza tion from 05% ethanolic ethyl acetate gives analytically pure 17B chloro 16oz methylyohimbane. MP. 310 to 313; [a] =-188, c.=0.5, pyridine.

Anal. for C H N Cl.Calcd.: C, 73.04; H, 7.66; N, 8.52; Cl, 10.78. Found: C, 73.05; H, 7.81; N, 8.59; Cl, 10.93.

Infrared spectra, 1123?: 750, 815, 2400 cmf U.V. spectra, A5233: 225.5 (e=36,000), 282 (e=7,000); A shoulder: 290 mu.

Into a solution of 3 g. 16rx-methylyohimbol(p-toluenesulfonyloxy)yohimbane in 40 ml. pyridine, under external cooling and under protection from moisture, is introduced anhydrous hydrogen fluoride until the volume is doubled. The reaction mixture is heated at 60 to 70 for four hours, allowed to stand for about 48 to 60 hours, poured with stirring onto 600 ml. crushed ice and basified with sodium hydroxide. The precipitate is collected on filter, washed with water and extracted with five 100 ml. portions of chloroform. The combined chloroform extracts are dried over sodium sulfate, filtered through supercel and evaporated to dryness to give 17B-fluoro- 16a-methylyohirnbane as a residue which after recrystallized from ethanol-ethyl acetate melts at 195 to 200; [a] =-145, c.=0.3.

Anal. for C H N F.Calcd.: N, 8.97. Found: N, 8.73.

Example 9.1 6 occh [oromethyl 7;8-ch loroyohim bane 20 ml. phosphorous oxychloride are added dropwise with stirring to a solution of 6.0 g. of 16u-(chloromethy1)- 17a-hydroxyyohimbane in 50 ml. of dry pyridine over a period of 40 minutes at 0. After standing at 20 to 25 C. for three hours, the reaction mixture is heated at 65 to 75 for three hours, cooled to 5", and poured onto 500 g. of ice-water. The solid which precipitates is filtered off, stirred with 10 ml. of 10% aqueous sodium hydroxide and 150 ml. of chloroform. The chloroform extract is dried over anhydrous sodium sulfate, and the solvent removed in vacuo. Trituration of the black residue with ml. of hot methanol, de-colorization with charcoal, and recrystallization from methanol-acetone gives 0.45 g. of 16a-(chloromethyl)-17fi-chloroyohimbane in the form of white, shiny needles, M.P. 259 to 263, [0c] =+11, c.=0.60, chloroform.

Anal. for C H N Cl .Calcd.: C, 66.11; H, 6.66; N, 7.71; Cl, 19.52: Found: C, 65.82; H, 6.92; N, 7.80; Cl, 19.67, 19.37.

Infrared spectra, 11?.733: 1335 (w.), 1285 (W.), 1100 (w.).

.V. spectra, A532,: 225 mu (6 =31,850), 280 my (e -6,750); shoulder: 289 (e=5,900); A min.: 246 (e=2,600).

It is to be understood that the foregoing detailed description is given merely by way ofillustration and that many variations may be made therein without departing from the spirit of our invention.

5 Having described our invention, what we desire to secure by Letters Patent is:

1. A compound selected from the group consisting of those having the formula:

and

H W W wherein R is a member of the group consisting of hydrogen and CHa-C- R is a member of the group consisting of hydrogen, 40 lower alkyl and chloromethyl, X is halogen and X is a member of the group consisting of chlorine and fluorine.

2. 17or-fluoroyohimbane. 3. 17a-brornoyohim'bane. 4. 17a-chloroyohimbane. 5. IO-acetyl-17a-ch'loroyohirnbane.

6. 17B-chlorol 6a-methylyohimbane. 7. 17p-fiuoro-16a-methylyohirnbane. 8. 1mac-chloromethyl-17fi-chloroyohimbane.

References Cited by the Examiner UNITED STATES PATENTS 3,046,279 6/62 Shavel et al. 260-287 FOREIGN PATENTS 222,546 7/59 Australia.

v OTHER REFERENCES Ban et al.: Tetrahedron Letters, No. 5 (Apr. 1962) pages 181-4. MacPhillamy et al.: Jour. Amer. Chem. Soc., vol. 77 (1955), pages 4335-4337 and 4340.

Robison et al.: Jour. Amer. Chem. Soc, vol. 83 (June 20, 1961), pages 2694, 2696, 2699.

WALTER A. MODANCE, Primary Examiner. N CH L S S- RI Ex miner. 

1. A COMPOUND SELECTED FROM THE GROUP CONSISTING OF THOSE HAVING THE FORMULA: 